using System;
using System.Linq;
using System.IO;
using System.Text;
using FEFTwiddler.Extensions;

namespace FEFTwiddler.Model
{
    /// <summary>
    /// A Fire Emblem Fates save file on disk
    /// </summary>
    public class SaveFile
    {
        #region Members and Properties

        protected string _inputFilePath;
        protected string _outputFilePath;

        protected Enums.SaveFileType _type;
        public Enums.SaveFileType Type
        {
            get { return _type; }
        }

        protected bool _isCompressed;
        public bool IsCompressed
        {
            get { return _isCompressed; }
        }

        protected byte[] _decompressedBytes;
        public byte[] DecompressedBytes
        {
            get { return _decompressedBytes;  }
            set { _decompressedBytes = value; }
        }

        protected byte[] _compMarker = new byte[] { 0x50, 0x4D, 0x4F, 0x43 }; // COMP backwards
        protected byte[] _indeMarker = new byte[] { 0x45, 0x44, 0x4E, 0x49 }; // INDE backwards

        #endregion

        public static SaveFile FromPath(string path)
        {
            var saveFile = new SaveFile();
            saveFile.ReadFromPath(path);
            return saveFile;
        }

        private void ReadFromPath(string path)
        {
            _inputFilePath = path;
            _outputFilePath = path;
            Read();
        }

        #region Read

        /// <summary>
        /// Read data into this object from the file at _inputFilePath
        /// </summary>
        public virtual void Read()
        {
            byte[] chunk;
            int length = GetFileLength();

            using (var fs = new FileStream(_inputFilePath, FileMode.Open, FileAccess.Read))
            using (var br = new BinaryReader(fs))
            {
                // Read the first four bytes
                chunk = new byte[4];
                br.Read(chunk, 0, 4);

                if (Enumerable.SequenceEqual(chunk, _compMarker))
                {
                    _isCompressed = true;
                    SetNonChapterType();

                    br.BaseStream.Seek(0x10, SeekOrigin.Begin);
                    byte[] compressedBytes = new byte[length - 0x10];
                    br.Read(compressedBytes, 0, length - 0x10);
                    _decompressedBytes = Decompress(compressedBytes);

                    return;
                }
                else if (Enumerable.SequenceEqual(chunk, _indeMarker))
                {
                    _isCompressed = false;
                    SetNonChapterType();

                    br.BaseStream.Seek(0, SeekOrigin.Begin);
                    _decompressedBytes = new byte[length];
                    br.Read(_decompressedBytes, 0, length);

                    return;
                }

                br.ReadBytes(0xBC); // Chapter header size (0xC0) minus the four bytes we already read

                chunk = new byte[4];
                br.Read(chunk, 0, 4);

                if (Enumerable.SequenceEqual(chunk, _compMarker))
                {
                    _isCompressed = true;
                    SetChapterType();

                    br.BaseStream.Seek(0, SeekOrigin.Begin);
                    byte[] header = new byte[0xC0];
                    br.Read(header, 0, 0xC0);

                    br.BaseStream.Seek(0xD0, SeekOrigin.Begin);
                    byte[] compressedBytes = new byte[length - 0xD0];
                    br.Read(compressedBytes, 0, length - 0xD0);

                    byte[] decompressedBytes = Decompress(compressedBytes);

                    _decompressedBytes = header.Concat(decompressedBytes).ToArray();

                    return;
                }
                else if (Enumerable.SequenceEqual(chunk, _indeMarker))
                {
                    _isCompressed = false;
                    SetChapterType();

                    br.BaseStream.Seek(0, SeekOrigin.Begin);
                    _decompressedBytes = new byte[length];
                    br.Read(_decompressedBytes, 0, length);

                    return;
                }

                throw new FileLoadException("File is not a valid Fire Emblem Fates save file");
            }
        }

        /// <remarks>Maybe replace this with smarter detection in the future</remarks>
        private void SetNonChapterType()
        {
            if (_inputFilePath.IndexOf("Exchange") > -1) _type = Enums.SaveFileType.Exchange;
            else if (_inputFilePath.IndexOf("Global") > -1) _type = Enums.SaveFileType.Global;
            else if (_inputFilePath.IndexOf("Rating") > -1) _type = Enums.SaveFileType.Rating;
            else if (_inputFilePath.IndexOf("Versus") > -1) _type = Enums.SaveFileType.Versus;
            else _type = Enums.SaveFileType.Unknown;
        }

        private void SetChapterType()
        {
            if (_inputFilePath.IndexOf("Map") > -1) _type = Enums.SaveFileType.Map;
            else _type = Enums.SaveFileType.Chapter;
        }

        private int GetFileLength()
        {
            return (int)(new FileInfo(_inputFilePath).Length);
        }

        #endregion

        #region Write

        /// <summary>
        /// Decompress this file to the original path plus _dec
        /// </summary>
        public void Decompress()
        {
            _isCompressed = false;
            _outputFilePath = _inputFilePath + "_dec";
            Write();
        }

        /// <summary>
        /// Compress this file to the original path, minus _dec if applicable
        /// </summary>
        public void Compress()
        {
            _isCompressed = true;
            if (_inputFilePath.Right(4) == "_dec")
            {
                _outputFilePath = _inputFilePath.Substring(0, _inputFilePath.Length - 4) ;
            }
            else
            {
                _outputFilePath = _inputFilePath;
            }
            Write();
        }

        /// <summary>
        /// Write data from this object into the file at _outputFilePath
        /// </summary>
        public virtual void Write()
        {
            if (_outputFilePath == null) _outputFilePath = _inputFilePath;

            WriteBackupFile();

            using (var fs = new FileStream(_outputFilePath, FileMode.Create, FileAccess.ReadWrite))
            using (var bw = new BinaryWriter(fs))
            {
                switch (_type)
                {
                    case Enums.SaveFileType.Chapter:
                    case Enums.SaveFileType.Map:
                        WriteChapterFile(bw); break;
                    case Enums.SaveFileType.Exchange: WriteExchangeFile(bw); break;
                    case Enums.SaveFileType.Global: WriteGlobalFile(bw); break;
                    case Enums.SaveFileType.Rating: WriteRatingFile(bw); break;
                    case Enums.SaveFileType.Versus: WriteVersusFile(bw); break;
                }
            }
        }

        private void WriteBackupFile()
        {
            var now = DateTime.Now;
            var backupFilePath = _outputFilePath + "_backup_" + now.ToString("yyyyMMdd_hhmmssfff");
            if (File.Exists(_outputFilePath))
            {
                File.Copy(_outputFilePath, backupFilePath);
                File.SetLastWriteTime(backupFilePath, now);
            }
        }

        private void WriteChapterFile(BinaryWriter bw)
        {
            if (_isCompressed)
            {
                bw.Write(DecompressedBytes, 0, 0xC0);
                bw.Write(GetChapterHeader(DecompressedBytes));
                bw.Write(Compress(DecompressedBytes.Skip(0xC0).ToArray()));
            }
            else
            {
                bw.Write(DecompressedBytes);
            }
        }

        private byte[] GetChapterHeader(byte[] decompressedBytes)
        {
            uint length = (uint)(decompressedBytes.Length - 0xC0);
            byte[] header = new byte[0x10];
            Array.Copy(Encoding.ASCII.GetBytes("PMOC"), header, 0x4);
            Array.Copy(BitConverter.GetBytes(2), 0, header, 0x4, 0x4); // 2 = Huffman-8 Compression.
            Array.Copy(BitConverter.GetBytes(length), 0, header, 0x8, 0x4);
            Array.Copy(BitConverter.GetBytes(GetChecksum(decompressedBytes)), 0, header, 0xC, 0x4); // CRC32 of Decompressed Data.
            return header;
        }

        private void WriteExchangeFile(BinaryWriter bw)
        {
            if (_isCompressed)
            {
                bw.Write(GetExchangeHeader(DecompressedBytes));
                bw.Write(Compress(DecompressedBytes.ToArray()));
            }
            else
            {
                bw.Write(DecompressedBytes);
            }
        }

        private byte[] GetExchangeHeader(byte[] decompressedBytes)
        {
            uint length = (uint)(decompressedBytes.Length);
            byte[] header = new byte[0x10];
            Array.Copy(Encoding.ASCII.GetBytes("PMOC"), header, 0x4);
            Array.Copy(BitConverter.GetBytes(2), 0, header, 0x4, 0x4); // 2 = Huffman-8 Compression.
            Array.Copy(BitConverter.GetBytes(length), 0, header, 0x8, 0x4);
            Array.Copy(BitConverter.GetBytes(GetChecksum(decompressedBytes)), 0, header, 0xC, 0x4); // CRC32 of Decompressed Data.
            return header;
        }

        private void WriteGlobalFile(BinaryWriter bw)
        {
            if (_isCompressed)
            {
                bw.Write(GetGlobalHeader(DecompressedBytes));
                bw.Write(Compress(DecompressedBytes.ToArray()));
            }
            else
            {
                bw.Write(DecompressedBytes);
            }
        }

        private byte[] GetGlobalHeader(byte[] decompressedBytes)
        {
            uint length = (uint)(decompressedBytes.Length);
            byte[] header = new byte[0x10];
            Array.Copy(Encoding.ASCII.GetBytes("PMOC"), header, 0x4);
            Array.Copy(BitConverter.GetBytes(2), 0, header, 0x4, 0x4); // 2 = Huffman-8 Compression.
            Array.Copy(BitConverter.GetBytes(length), 0, header, 0x8, 0x4);
            Array.Copy(BitConverter.GetBytes(GetChecksum(decompressedBytes)), 0, header, 0xC, 0x4); // CRC32 of Decompressed Data.
            return header;
        }

        private void WriteRatingFile(BinaryWriter bw)
        {
            throw new NotImplementedException();
        }

        private void WriteVersusFile(BinaryWriter bw)
        {
            if (_isCompressed)
            {
                bw.Write(GetVersusHeader(DecompressedBytes));
                bw.Write(Compress(DecompressedBytes.ToArray()));
            }
            else
            {
                bw.Write(DecompressedBytes);
            }
        }

        private byte[] GetVersusHeader(byte[] decompressedBytes)
        {
            uint length = (uint)(decompressedBytes.Length);
            byte[] header = new byte[0x10];
            Array.Copy(Encoding.ASCII.GetBytes("PMOC"), header, 0x4);
            Array.Copy(BitConverter.GetBytes(2), 0, header, 0x4, 0x4); // 2 = Huffman-8 Compression.
            Array.Copy(BitConverter.GetBytes(length), 0, header, 0x8, 0x4);
            Array.Copy(BitConverter.GetBytes(GetChecksum(decompressedBytes)), 0, header, 0xC, 0x4); // CRC32 of Decompressed Data.
            return header;
        }

        /// <remarks>Taken directly from FEST. "It's just CRC32."</remarks>
        private static uint GetChecksum(byte[] data)
        {
            uint checksum = 0xFFFFFFFF;
            uint length = (uint)data.Length;
            uint[] table = { 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d };
            if (length > 0)
            {
                int ofs = -1;
                if (length % 2 == 1)
                {
                    ofs++;
                    checksum = table[(byte)(data[ofs] ^ (checksum & 0xFF))] ^ (checksum >> 8);
                }
                uint v12;
                for (uint i = length >> 1; i > 0; checksum = table[(byte)(data[ofs] ^ (v12 & 0xFF))] ^ (v12 >> 8))
                {
                    i--;
                    int v10 = (byte)(data[ofs + 1] ^ (checksum & 0xFF));
                    ofs += 2;
                    v12 = table[v10] ^ (checksum >> 8);
                }
            }
            return ~checksum;
        }

        private byte[] Compress(byte[] dec)
        {
            return new Utils.Huffman8().Compress(dec);
        }

        private byte[] Decompress(byte[] cmp)
        {
            return new Utils.Huffman8().Decompress(cmp);
        }

        #endregion
    }
}
